A method of forming a protection film for a safety valve element, a safety valve element which is coated with a protection film, a closing plate for battery using same and a closed battery using same
The present invention relates to a method of forming a protection film of a safety valve element, a safety valve element covered with a protection film, and a battery using same which prevents from corrosion of a metal part of a safety valve element used for bursting-proof of a closed battery.
A closed battery using an alkali metal like lithium as a material for positive and negative electrode has been widely used in recent years. These batteries need sealed structure so that an alkali metal like lithium may not react with moisture in an atmosphere, but a completely closed structure sometimes causes a bursting of battery provoked abnormally elevated pressure in the battery when the battery is exposed to high temperature or it is inappropriately handled at the charge or discharge.
It is disclosed that a closing plate for a battery provided with a bursting-proof mechanism or a safety valve for releasing a pressure in a battery when it is abnormally elevated.
For example, Japanese Patent Laid-open Publication No.HEI-5-84025 discloses a safety valve device for a closed battery which provide a gas releasing opening in a positive electrode terminal constituting a closing plate for a battery and a metal foil welded for bursting-proof.
In this closing plate for a battery, when a pressure in a battery is elevated, a metal foil for bursting-proof ruptures so that a pressure releases through a gas releasing opening applied in a positive electrode terminal.
When electrolyte is filled up in a battery container, electrolyte sometimes scatters and adheres the outside of it. Especially, in case of lithium ion battery, a non-aqueous electrolyte including lithium fluoride as a supporting electrolyte is used for electrolyte.
This fluoride does not attack a metal part of a battery container and a safety valve, but it has strong corrosion so as to absorb moisture in atmosphere and to change into hydrofluoric acid.
For this reason, it is a problem that an electrolyte scatters and adhere an outside of a battery container, especially a metal a foil of a safety valve element, and that a thin metal foil is perforated by corrosion.
The present invention provides a method of forming a protection film of a safety valve element for a closed battery, a safety valve element covered by a protect film, a closing plate using same and a closed battery using same which prevents from corrosion of a metal part by covering the safety valve element for battery by a protection film.
The present invention is a method of forming a protection film of a safety valve element for a battery comprising a metal substrate having perforated pores and a metal foil laminated on said metal substrate so as to cover said perforated pores, wherein an organic coating is coated on at least one side of it.
Further, it is a method of forming a protection film of a safety valve element of a battery comprising a metal substrate having perforated pores and a metal foil laminated on said metal substrate so as to cover said perforated pores, wherein an organic resin film is laminated on at least one side of it.
Furthermore, it is a method of forming a protection film of a safety valve element of a battery comprising a metal substrate having perforated pores and a metal foil laminated on said metal substrate so as to cover said perforated pores, wherein an organic coating is coated on at least one side of covering portions of said metal foil.
Further, it is a method of forming a protection film of a safety valve element for a battery, wherein an organic coating is coated on a safety valve element for a battery comprising a metal substrate having perforated pores and a metal foil laminated on said metal substrate so as to cover said perforated pores after said safety valve element for a battery is applied on a closing plate for a battery container having a perforated pore which is to be a valve opening of a safety valve so that said perforated pores of said metal substrate of safety valve element for a battery and said perforated pore of said closing plate are connected through, and said metal substrate and said closing plate are adhered together using adhering means so that both adhere around said perforated pore of said closing plate, and it is characterized that said means is laser beam welding.
Further, the present invention is a safety valve element for a battery comprising a metal substrate having perforated pores and a metal foil laminated on said metal so as to cover said perforated pores, wherein a protection film is covered on at least one side of said safety valve element for a battery.
It is characterized that said protection film is a coated film of an organic coating or a laminated film of an organic resin film.
Further, it is a safety valve element for a battery comprising a metal substrate having perforated pore or first hole extending therethrouh, and a metal foil laminated on said metal substrate so as to cover said perforated pores, wherein a protection film is covered on at least one side of covering portions of said metal foil of a safety valve element for a battery, and it is characterized that said protection film is a coated film of an organic coating.
Further, the present invention is a closing plate, wherein said safety valve element for a battery is applied on a closing plate for a battery container having a perforated pore or second hole extending therethrough which is to be a valve opening of a safety valve so that said perforated pore of said metal substrate of safety valve element for a battery and said perforated pore of said closing plate are connected through, and said metal substrate and said closing plate are adhered together using adhering means so that both adhere around said perforated pore of said closing plate, or a closing plate, wherein said safety valve element for a battery comprising a metal substrate having perforated pores and a metal foil laminated on said metal substrate so as to cover said perforated pores is applied on a closing plate for a battery container having a perforate pore which is to be a valve opening of a safety valve so that said perforated pores of said metal substrate of safety valve element for a battery and said perforated pore of said closing plate are connected through, and said metal substrate and said closing plate are adhered together using adhering means so that both adhere around said perforated pore of said closing plate, and after that an organic coating is coated on said safety valve element for a battery, and it is characterized that said adhering means is laser beam welding.
Furthermore, the present invention is a closed battery, wherein an electrode comprising a positive electrode, a negative electrode and a separator is packed with electrolyte into a battery container and an opening portion of said battery container is closed so that said a closing plate for battery is put not and fixed around inner circumference of said opening portion of said battery container.